Pyrethrins and Synthetic Pyrethroids

PYRETHRINS AND SYNTHETIC PYRETHROIDS
  • Lipophilic/ rapidly absorbed, distributed  and excreted - excellent for knock down effect, has poor residual activity(instability) hence, is of  low mammalian toxicity
  • Pyrethrin I is most active ingredient for killing insects  and Pyrethrin II for rapid insect knock down
  • Pyrethrins acts on insect’s CNS by exciting the cell membranes resulting in extended depolarization
  • Prolongation of activity can occur when the compound is microcapsulated or stabilized
  • Certain pyrethrin preparation contain piperonyl butoxide which acts as synergist by helping to prevent pyrethrin break down by microsomal function oxidase(MFO) system in insects
  • Synthetic pyrethroids are more stable with higher potency.  It  can be combined with synergists like piperonyl butoxide
  • Common pyrethroids include bioallethrin, cypermethrin, deltamethrin, fenvalerate, flumethrin, lambdacyhalothrin, phenothrin and permethrin

Mode of action

  • Interference with Na channels of the parasite nerve axons resulting in delayed repolarization and repetitive discharge of the nerve

Type II

  • Also act on Na+ gate but without causing repetitive discharge lethal activity of pyrethroids involves both peripheral and central neurons while the knock down effect is produced by peripheral neuronal effects only
  • Pour ons, spot on, spray, dip, topical powder, spray, ear tags etc 
Last modified: Monday, 9 May 2011, 9:56 AM